No. 109.] 



87 



Rhtxchonella. pleiopleuka. 



Waldheimia GLOBOSA. 



Pal. N.Y. Vol.iii, pi. 36, f. 1. 



IShell subglobose, oval : ventral valve a little larger tban the 

 opposite one, most gibbous in the umbonial region ; beak promi- 

 nent, rounded and arched, perforate at the extremity by a round 

 aperture) one side of which is formed by a deltidium : dorsal 



